Currently, food colours are manufactured from organic/inorganic synthetic sources and are considered to be potentially harmful. Pigments and bioactive compounds extracted from fruits or plant materials are widely used in the food industry as functional ingredients. Many other bioactive ingredients are also well perceived by consumers for their beneficial properties, but their application in e.g. food products is either difficult or provides poor bioavailability. In addition to that, current extraction techniques afford the desired ingredients in very low yield and lead frequently to some deterioration of the genuine properties of the extracted ingredients. Betalains, a group of naturally occurring pigments, include the betacyanins which are red-violet and the betaxanthins which are yellow. Betalains have been detected only in red-violet, orange and yellow pigmented botanical species belonging to related families of the order caryophyllales. Of the numerous natural sources of the betalains, red beet and prickly pear are the only edibles containing high concentrations of these pigments. The betacyanins are derived from two aglycons, betanin and iso-betanidin. Betanin is a betanidin 5-O-β glucoside. Betanidin contains an ortho-diphenol group, which is suspected to be a very good electron donor or hydrogen donor, working as an active antioxidant. In addition to their antioxidative effects, betanin and betanidin are cationized molecules which may increase their protective effects on cells and organelles against oxidation. Cell and organelle membranes are negatively charged and anionic sites on the cell surface have been shown to exhibit strong affinity for cationic agents.
Dragon fruit which is known as pitaya, pitahaya, pitajaya, or pitaya roja belongs to the Hylocereus sp. from the Cactaceae family (Luders and McMahon, 2006). The usage of purple-flesh (red-violet) dragon fruit (Hylocereus polyrhizus) as a good source of betalains has been highlighted by several authors (Stintzing et al., 2002; Wybraniec et al., 2001). The colour of betalain is close to that of anthocyanins but is three times stronger (Stinzing and Carle, 2007). Betalains are also more water soluble than the anthocyanins (Stintzing et al., 2006). They make a good choice for colouring of low-acid foods because, compared to anthocyanins, they maintain their colour in the pH range of 3 to 7 (Stintzing and Carle, 2004).
Dragon fruit can be powdered to have a longer shelf life and therefore could be easily and readily available and served as a good source of betalain rich functional food ingredient for addition into food products as natural color or having instant properties. In addition, the powder form can be very stable due to its low water activity and therefore low biochemical reactions. Spray drying of fruits which contain high sugar and organic acid contents is difficult. These compositions have a sticky behavior during spray drying. Stickiness depends on the properties of the materials and also involved the inlet variables applied in the spray drying process. Deposition is another problem that arises from the stickiness and the design of the drier. If the size of the chamber is large enough, there will not be deposition problem but because of economic factors, the size of the chamber would be limited to a suitable size. Therefore, the stickiness and deposition should be solved by other methods (Truong et al., 2005). The sticky behavior of sugar and acid rich materials is related to the low molecular weight of sugars (fructose, glucose and sucrose) and organic acids (citric, malic and tartaric acid) whereby 90% of solids in fruits are of these compounds (Bhandari et al., 1997). Some additives such as maltodextrin have been used to reduce the stickiness and deposition in spray drying of foods such as blackcurrant (Bhandari et al., 1993), honey (Bhandari et al., 1997), tamarind (Truong, 1994), watermelon (Quek et al., 2007), and pineapple (Abadio et al., 2004). Different types of maltodextrin with dextrose equivalent (DE) ranging from 5 up to 40 are available commercially. The higher the DE of a maltodextrin, the lower is the chain length of its glucose polymer. Maltodextrins are the most common of additives used for drying of fruit powders and usually, the fractions of these carriers are 40 to 60% but higher amounts can also be used (Masters, 1994). There is a complex interaction between spray drier apparatus, process, and product parameters (solid content, viscosity, and temperature) which affect the quality of the powder. The most effective factors in a spray drying process are feed flow rate, inlet and outlet air temperatures, atomizer speed, feed concentration, feed temperature, and inlet air flow rate (Chegini, & Ghobadian, 2005). The aim of this study is to investigate the relationship between inlet air temperature, outlet air temperature, and maltodextrin concentration as important factors in spray drying of dragon fruit and to evaluate their effects on the betalain content and physical properties of the powder produced.
Fruits are usually rich in reducing sugars, making the drying of their juice and handling of their powder very difficult. There may also be lost of some colour in the fruit powder or low stability and short shelf life of the powder during storage. A large number of extraction and concentration techniques are already known. The techniques, however, may be costly. In addition, there may be some technical problems at the time of applying the fruit powder as natural colour. It is thus an object of the present invention to address the above problems by providing a simple and cheap method for producing a natural colorant (preferably known also as betalain) from a fruit with improved stability, miscibility, dispersibility in aqueous systems and, also, with enhanced bioavailability as compared to similar extracts from the prior art. This invention relates to natural colorants as a bioactive ingredient preferably used in foodstuffs, neutraceuticals, pharmaceuticals and cosmetics. The natural colorant is in a form of powder and which the powder is suitable to be used as an additive agent, in foodstuffs which include dairy and ice-cream products, jellies, snacks, confectionaries, alcoholic and non-alcoholic beverages, pharmaceuticals and cosmetics which contain betalain especially. Moreover, the present invention relates the natural colorants containing betalains obtained from fruits, preferably dragon fruit (Hylocereus polyrhizus), useful for prevention and treatment of disorders and diseases that are due to oxidative stress, especially vascular diseases or the compositions may be pharmaceutical compositions containing, as an active ingredient, betacyanins that are produced from dragon fruit (Hylocereus polyrhizus). The advantage of the present invention also relates to a cost effective method and manufacturing method of foodstuff or pharmaceutical or cosmetic products containing betalain as a natural colorant obtained from dragon fruit (Hylocereus polyrhizus 